Kyoukan

A boy is very bad in studies and he is sent to a special cram school. Hell reveals before him - escape is impossible, students have to study from morning till night and teachers are very experienced and strict. However it's written with small letters in the bottom that all the teachers are females and they attend students 24 hours a day. Yeah! It may turn out much more interesting that it seemed to be. The girl who likes him decides to follow him and prevent any misconduct that may arise!

[From vndbreview]